Bevel gear cutting machine



April 14, T953 P. ASCHWANDEN 2,634,657

I BEVEL. GEAR CUTTING MACHINE Filed April 6, 1948 4 Sheets-Sheet 1 Jmnw,

P. ASCHWANDEN BEVEL GEAR CUTTING MACHINE pril 14, 1953 Filed April 6, 1

I 4 Sheets-Sheet 2 April 14, 1953 4 ASCHWAN DEN BEVEL GEAR CUTTING MACHINE 4 Sheets-Sheet 5 Filed April 6, 1948 April 14, 1953 P. ASCHWANDEN 2,634,657

BEIVEL. GEAR CUTTING MACHINE Filed April 6, 1948 4 Sheets-Sheet 4 FIG.3

INVENTOR 'for other machining methods.

Patented Apr. 14, 1953 2, 34,657 BEVELGEAR; CUTTING MACHINE Paul Aschwanden, Zurich, Switzerlan d, assignor to Verwaltungs'gesellschaft der Werkzeugmaschinenfabrik Qerlikon,

-zerland Zurich-Qerlikon, Switnnli afi nnt 6, 8.Ser n-- 9 22 In Switzerland April 11 941 (own-5) reclaims.

This invention relates to machines for cutting bevel Wheels, particularly to that type operating according to the continuous dividing and generating process, but which "may also be -used has as object the provision of a completely automatic control of the machine, once this latter has been set for machining a gear blank, re-

quiring very little attendance during the entire machining operation'for the production of ,a'bevel wheel.

*Gear cutting machines of the above type usu- .-ally comprise a work head unit carrying the gear 'blank and a. generating unit including a generating drum which carries the tool, the two units being arranged for relative movement towards and away from each other into 1 operating position or into a position ofrest in whichthe various adjustable members of the machine are set for the next following cutting operation.

According to the invention the machine comprises a pressure fluid control system using a single operating lever coupled with av main control valve for the pressure {fluid to control the main drive of the machine, the advance and I return movement of the tool relatively to the gear blank in;the direction of the axis of the ideal crown wheel of the gear to be cut, and also the feed or generating gearof the machine.

' The same operating lever may be used'to control a rapid speed "for accelerating thereturn roll of the generating drum to its startingvposition when the tool has finished its generating feed motion at the end of a cutting operation.

-An auxiliary control valve for the pressure fluid can be disposed in the generating unit for cooperation with abutments on the generatingdrum which operate the control valve in suchimanner that for example an increased feed or generating motion speed is obtained after the tool has worked out the full depths of the tooth space on the blank and that the operating lever of the main control valve is automatically moved to the position of starting the above mentioned increased return speed or for stopping' themain drive after a cutting operation has been terminated.

, A preferred example of the invention is illustrated in the accompanying drawings.

Fig. 1 is a general viewofa machine forcutting bevel gears, operatingaccording to the continuous dividing and generating process;

Figures 2a and 2b are a diagrammatic representation o the ydraul c. contr s te pfth m chine.

The invention Figure 3 is a diagrammatic representation of themovable driving elements, of the machine.

In Fig. 1 the numeral l indicates the horizontally .movable head stock of the machine which contains a rotatable screw carrying the clamping chuck 16| for the work piece or gear blank a. The head stock Iis carried by a pivoting table) ,yvhich.can effect an angular movement in a'horizontal plane about a vertical axis. Ahand wheel H2 which actuates a gear meshing with a fixed gear segment 62 serves for adjusting the pivoting table. The tool carrier 3 is disposed "in a cross slide 4 themovefnent of which serves to adjust the excent'ricity of the tool .axi'srelatively to the axis of the blank (1. The cross slide dis carried in 'turn'by the gene'rating drum .5 having a peripheral gear and which isrotatably disposedin the generating unit'fi, whichis horizontally movable on'the machine bed 1. Q8 indicates an overhead tie which is .mounted onthe work head unit I 'and on the generating unit 6 so as tobe 'movable relatively thereto and to be lockedtothesetwounits, in order to constitute a supplementary connection of thesetwo parts in operating position to increase the rigidity of the machine and accordingly the precision of themachining operation.

The drive of themachine isefiected by .a main driving motor M (Fig. 3) which imparts rotation by the intermediary of a belt 45, clutches and change speed gear43 to the tool b,,and by the intermediary oflan indexing gear H0 to the chuck 6| (Fig. .3) The'tra nsmission to the index'ing gear Ilil includes a differential gear "46. A generating gear W operatively connects the differential gear 46 with the generating drum 5. A bevel gear f ll transmits movement from the differentialgear by the. intermediary of a feed gear S and. a, clutch 3l to the generating gear 1 represented in my copending application Ser.;No.

As shown inFig. 2a, the maincontrol'lever 9 can be brought to five positipnsi'on; II, III, IV. f It is pivotally mountfidat. 63,.and its movenien't'is transmitted by transmission wheels -30 to theaxjis of the main, control. valve 29 formed as a retating piston valve. For the'sake'of clearness of its operation, this control valve is diagrammatically represented in drawn apart portions; in reality it forms a single piston provided with the corresponding flow ducts for the control fluid. This valve is connected by a conduit PI to the pressure conduit P fed with pressure oil from a gear pump 39 through a pressure valve 64. The suction side of the pump 39 is connected by the conduit 65 to filtering devices 40 which are disposed in the machine bed I serving as oil reservoir.

An auxiliary control valve 2| also formed as rotating piston valve is disposed in the generating unit 6. This auxiliary control valve is represented in the same manner as the main valve 29, for the sake of clearness, in drawn apart portions. It is connected by the flexible conduit P2 to the pressure conduit P of the pump 39. On the axis of the control valve 2I is seated a star-shaped cam or Maltese cross 20 which cooperates with three adjustably fixed cam driving abutments I'I, I8 and I9 on the generating drum 5.

When starting the machine, the control lever 9 is in the position as represented in Fig. 2a. By actuation of the electric contacts 66 (Fig. 1) the main drive motor M and the pressure oil pump 39 are started. The pump 39 delivers pressure oil through the conduit P into the conduits PI and P2, as well as into a conduit P3 leading to a control valve 42 for the clamping chuck 6| of the blank a. This valve 42 is moved by a lever 61. When the blank is chucked the valve 42 is in the position represented in Fig. 2b, in which the pressure conduit P3 is connected to a conduit PSFI which delivers pressure oil into a cylinder 68, so as to maintain a piston 4! connected with the clamping chuck in the represented position in which the gear blankis chucked. When the blank is released the valve 42 is situated in a position turned through 90 in which it connects the pressure conduit P3 with the conduit PSFZ which delivers pressure oil to the other side of the piston GI and moves this latter towards the left, while the conduit PSFI is connected to the discharge Po leading to the fluid reservoir.

Pressure oil from the conduit PI delivering into the annular chamber 29 of the valve 29 arrives through the duct 69 of the control valve into the conduit PA2 which delivers pressure to a braking device 31 of the main drive and applies the brake, while the main drive clutch 36 is connected with the central discharge P0 of the control valve 29 through the conduit PAI and is out of operation. The head stock I of the machine has been brought to an exactly predetermined position by actuation of the hand wheels HI and H2 and clamped in this position. The tool I) is fixed to the tool carrier 3 and adjusted by means of the cross slide 4 to the predetermined eccentric position relatively to the axis of the generating drum 5 and is then clamped to the generating drum. The generating unit 6 is secured to a piston 28 which is subjected to fluid pressure by a conduit P4 communicating continuously with the pressure conduit PI, the pressure acting on the right hand face of the piston which is accordingly moved towards the left in Fig. 2a. In this position of the piston 28, the generating unit together with the tool is removed from the head stock I in the direction of the axis of the imaginary crown wheel of the gear to be made, and owing to the disengaged clutch 36 the main driving gear as well as the indexing gear H0 and the feed gear S and the generating gear W are at rest.

When now the control lever 9 is brought by 4 hand to the position I the main control valve 29 turns through one step, owing to the transmission wheels 30, in the direction of the arrow 0. This movement causes the conduit PA2 to be shut on from pressure and to be connected to the central discharge P0 of the control valve 29, so as to release the brake 31. The conduit PAI is now connected by the duct I0 of the control valve with the pressure conduit PI, whereby the main drive clutch 36 becomes engaged. The main driving gear and the indexing gear I I0 are operatively connected with the previously started driving motor and the tool as Well as the blank start to rotate.

The control valve 2I in the generating unit 6 is now in the represented position of rest. The conduit PEA is connected by the duct 82 of this valve with the pressure conduit P2 delivering fluid under pressure to the annular chamber 2 I of the valve. The oil pressure acts on a pilot piston 34 which controls an electric switch E of a motor for a rapid speed gear the function of which is described later and maintains the piston in the represented position in which the right side of a switch operating piston 35 is connected by the conduit 83 with the discharge Po, so that the spring 84 moves the piston 35 towards the right and the switch E is operated to cut-ofl the circuit of the rapid speed motor.

The control lever 9 is now brought to the position II and the main control valve 29 rotated through a further step. The conduit PAI leading to the main drive clutch 36 remains connected by the ducts ID and II with the pressure conduit PI and the conduit PA2 leading to the brake 31 remains connected to the discharge P0. The conduit PWS is connected by the duct I2 of the control valve 29 with the pressure conduit PI. A non-return valve 26 is moved towards the left and the conduits PWSI and PWSZ receive pressure. The conduit PWSI leading to a piston valve 2'! places this valve under pressure and moves the piston to close the discharge Po which communicated until now with the chamber 28' of the piston 28. Pressure fluid therefor arrives by the conduit PWS2 on the left side of the piston 28 and owing to the larger piston surface on this side, the piston 28 is moved towards the right whereby the generating unit 6 together with the tool 22 is moved in the direction of the axis of the imaginary crown wheel towards the gear blank to be machined.

In the most advanced position of the generating unit which is determined by an adjustable abutment I3 on the bed of the machine, the outer edges of the cutting blades of the tool *1) are situated in the plane of the bottom of the tooth spaces of the gear to be cut, at the point of engagement of the tool blades and the work piece, or in the plane of the outer edges of the teeth of the imaginary crown wheel. However, the blades have not yet any cutting action, since the generating drum 5 is still rolled out of the position in which the blades become efiective. The advancing movement of the generating unit 6 is limited by the adjustable abutment 73 on the bed of the machine, which can be displaced by means of a handwheel II (Fig. 1 and a Worm gear Ma.

The pressure in conduit PWS is communicated to a piston valve 25 carried by the generating unit 6 and moves this piston towards the right in Fig. 2.1 so as to interrupt the previously existing communication between the discharge P0 and a conduit PK. When the advancing generating unit 6 makes contact with the abutment 73 a sliding rod I4 carried by the generating unit and bearcommunicates pressure actuates an electric switch EL in the circuit of an electric motor driving a cooling agent pump.

:cumferential groove the switch E remains not 2| with the pressure conduit P2.

"amass? ing against the abutment is moved towards the left and rocks a lever 15 which in turn moves a small piston .24 towards the right. Pressure fluid thus arrives from conduit PWS in the conduit PK to which are connected the conduits PKG and PKEB. The conduit PKG leads fluid under pressure to a plurality of clamping pistons K6 which by means ofwedges 'l'l lockithe generating unit 5 in its advanced position which is the working position, by clamping it to the bed of the machine as soon as it arrives against the abutment 13. The conduit PK8 communicates the pressure to a clamping piston K8 which operates a clamping wedge '18 for locking the overhead tie 8 to the generating unit 6. The conduit PKii also to a piston 38 which When a pre selector switch 66 (Fig. 1) has been actuated to close thecircuit, the motor is started and drives the pump to deliver a jet of cooling liquid against the tool which will soon begin its :cutting action. When a material as for example cast iron is worked which does not need a cooling fluid, the pre-selector switch 65' is not moved to on-position so that an actuation of the switch EL by the moved piston 38 cannot close the motor circuit.

After clamp-ing the generating unit 6 and the overhead tie 8, the machine is ready to start the cutting operation on the blank. The control leverfi is now moved to the position III, in which its lower end 19 abuts against a shut-down piston '32.

through a further step. The conduits PAI and The control valve 29 is accordingly turned PWS remain under pressure. The clutch 3| whichhas been connected until now by the conduit 82 to the central discharge P of the control valve 29, is now connected by the duct 8| of the valve to the pressure chamber 29' and the feed motion and generating gears S and W of the machine start to operate. This gear causes the rotation of the generating drum about the axis of the imaginary crown wheel of the gear wheel to be cut and imparts the required well known supplementary movement of rotation also to the blank, which movement is the same as if the imaginary crown wheel were in mesh with the gear 'to be cut into the blank. Owing to rotation of the generating drum in the direction of the arrow at the tool approaches the work-piece and eventually starts to cut into the blank.

The generating drum 5 is provided with a cir- 8| in which are engaged three circumferentially adjustable abutmen'ts ll, i8 and I9. The abutment |9 is so adjusted that at the beginning of the movement of the generating drum 5 it engages immediately with one of the slots of the Maltese cross 29 carried by the axis of the control valve 2| and turns this latter through a quarter of one revolution in the direction of the arrow 6. This quarter turn has no action on the operation of the machine. The conduit PEA is connected with the central discharge P0 of the'controlvalve 2|. The pressure on the pilot piston 34 for the switch E is interrupted and the spring 85 moves the piston towards the right. The conduit 83, however, is now connected by the conduit PE with the central discharge P0 of the main control valve 28 and actuated. The conduit PVSZ is connected by the duct 8'! of the valve The oil pressure acts accordingly on the right side of a piston |4 for the control of an automatic increase of the 'rnotion speed to be moved in its. right hand position,

feed speed can the adjusted in the beginning "by means of a hand-wheel 12 (Fig. v.1) connected with a pinion 1|2 whichbperates a train of gears controlling the speed 'variator of the .feed motion drive. During the adjustment of .the .feed motion speed the wheel |2 can be disengaged from a transmission wheel 13 by :means of apush member iii, the wheel |3 meshing with a gear rack of the piston is. The desired increase of feed motion speed for the final period of the generating rolling movement :is adjusted by means 'of a hand-wheel l5 and ismade visible on a graduation 8'9. The hand-wheel l5 moves a stop 88 cooperating with an abutment 9B of the piston i i as will be described later.

The gen-erating'drumt continues its movement of rotation and the tool 1b engages-deeper into the blank until the cutting blades .of the tool have cutout the entire depth of the tooth spaces from the blank. At this moment the cutting of material from the blank practically finished, the tool must only complete its generating rolling movement and an'unimp-o-rtant cutting operation is still eflected along the tooth flanks only. In order to save time it is therefore possible to increase the feed motion or generating speed of the generating drum and accordingly also the supplementary speed imparted to the blank. For eiiecting the required control operations to obtain the increased generating speed the second abutment l8 has been correspondingly adjusted along the groove 8| of the generating drum 5. This second abutment now engages the Maltese cross 26 and imparts a further quarter of one revolution to the control valve 2|. .As result of this further step of the valve the conduit PVS| receives pressure-by beingconnected at the auxiliary piston 22 to the conduit 9| which now communicates by the duct 92 of the control valve 2| with the pressure chamber 2|. The conduit PVS2 communicates with the central discharge P0 of the control valve.2| causing the piston it of the control device for the increase of the feed towards the right until the abutment 90 of the piston bears against the the desired increase of feed motion speed. The

pressure in the conduit PVSI has moved the auxiliary piston 23 towards the right. The conduit PEA is still connected to the discharge Po by the valve 2|, while the conduit PVA is connected .by the displaced auxiliary piston 23 with the central discharge P0 of the control valve 2 I.

When the tool hasfinished its generating ieed movement at increased speed, the third cam ll engages the Maltese cross 2t and imparts a further quarter turn to the control valve 2| in the direction of the arrow e. Now the conduit PVS2 is connected again by a duct 92 of the control valve 2| with the pressure conduit P2, while the conduit .PVS! is connected by the auxiliary piston 22 and the conduit 9| with the discharge P0 of thevalve 2|. The control piston It for the increased feed motion speed accordingly returns into the position shown in Fig. 2a, and causes the increased .feed motion speed to be disconnected. The conduit 93 leading to the control piston 23 is now connected by the duct 94 of the control valve 2| with the pressure conduit P2, and since the piston 23 is fluid pressure arrives in the conduit PVA which leads to the pilot piston-.33 of the shut-down-piston 32 which coacts with .the main operating .lever 9. The piston "remains connected with the discharge.

"33 is moved against the action of its spring 95 and pressure oil arrives on the left end of the piston 32 the other end of which makes contact with the lower end 19 of the control lever 9 in the position III. The piston 32 is displaced towards the right in the cylinder 96 by the pressure fluid until it arrives against a shoulder 91 and while acting against the lower end 19 of the lever 9 this latter is automatically returned to its starting position 0. The return of the lever 9 results in the return of the main control valve 29 to the starting position represented in Fig. 2a. The conduit 80 leading to the clutch of the feed motion gear is again connected with the discharge Po; the clutch is released and the feed or generating movement stops.

The conduit PWS to the non-return valve 26 is connected at the main control valve 29 with the'discharge P0. The pressure on the left side of the control piston 25 for the clamping members K6 and KB decreases, the pistons 24 and 25 are moved towards the left by their springs Hill and HM, and the conduit PK is connected with the discharge Po by the duct |02 which is now open. The pressure in the conduits PKG and PKB decreases and the clamping members K of the generating unit 6 and K8 of the over head tie 8 are released. The piston 38 is released from hydraulic pressure and returns by the action of its spring I03 into the represented position, while the switch EL for the motor of the cooling liquid pump is operated to stop the motor. At the same time the pistons 26 and 21 have been displaced towards the right by their respective springs 98 and 99 into the represented positions, and the left side of the main piston 28 of the generating unit 6 is thus connected with the discharge Po. Since the conduit P4 is always under pressure, the main piston 28 is displaced towards the left and returns the generating unit with the tool to the position of rest. The conduit PA| is connected again with the discharge P0 at the main control valve 29: the clutch in the main drive of the machine is released while the conduit PAZ which is again under pressure applies the brake 31. The main drive gear and the indexing gear of the machine are now stopped.

The main control lever 9 can now be brought by hand to a position IV. In the corresponding position of the valve 29 the conduit PE for the control of the rapid speed switch E is connected by the duct 8| of the control valve 29 with the pressure conduit Pl, while the conduit PEA is connected with the discharge at the control valve 2! which is still in its third position of operation. The piston 34 is accordingly moved towards the right and fluid'pressure acting through the conduit 83 on the piston 35 moves this latter against the action of its spring 84 to operate the electric switch E for a rapid speed motor. This motor is coupled with the feed motion or generating gear of the machine and drives this gear and the indexing gear at rapid speed and in the direction opposed to the direction of movement obtained by the main driving motor. The generating drum is now rolled back at increased speed to the ready-for-operation position and also the blank effects a return rotation.

In this position of rapid return speed the brake 31 of the main drive remains connected to the pressure conduit Pl through the conduit PA2 and the duct 12 of the valve 29, and the conduit PAI leading to the main drive clutch 36 The gencrating drum 5 turning in opposite direction, the movements of the auxiliary valve 2| produced by the three abutments I1, I 8 and 9 are efiected in reversed succession than during the generating rolling movement of the generating drum 5, and the cam ll engages first the Maltese cross 20 and turns this latter and the control valve 2| through one step in the direction opposite to the arrow e, and afterwards thecam l8 engages the Maltese cross and turns the control valve through a further quarter turn backwards. These two reverse movements of the control valve 2| do not initiate any control functions, the conduit PEA to the piston 34 remains connected to the discharge at the valve 2|, and the piston remains in its displaced right hand position. The conduit PE is under pressure which acts through the conduit 83 on the switch actuating piston 35 which maintains the rapid speed motor switch in switched-on position.

After the cam H! has also engaged the Maltese cross 26 and returned this latter through a further step, the control valve 2| is again in its position of rest. Now the conduit PEA is connected by the duct 82 of the valve 2| with the pressure conduit P2, the pilot piston 34 for the switch E is moved into the represented position towards the left and the conduit 83 is connected with the discharge Po at the piston 34. The spring 84 moves the piston 35 towards the right and the switch E for the rapid speed motor is actuated to shut the motor down. The control lever 9 can now be brought by hand to its starting position 0, so that the main control valve 29 is also returned to its starting position and the generating drum 5 will be in position ready for a new cutting operation. Since the abutment l9 has engaged and turned the Maltese cross 20 immediately at the beginning of the rolling movement of the generating drum 5, the generating drum 5 is again in its exact starting position as soon as the abutment I9 has returned the Maltese cross and. the rapid speed gear has been stopped. It will be remarked that the return of the generating drum to its starting position is efiected by a return rolling movement of the drum and not by a complete revolution of the same in the direction of the generating movement. This oiTers the advantage that when a gear blank is subjected to several successive machining operations, the same portions of all gears taking part in the driving and generating movements are meshing with each'other during each cutting operation, so as to avoid that any possible small errors in the gearing may become effective at different positions of the tool relatively to the blank.

Already during the rapid speed for the reverse roll of the generating drum the machined blank can be removed from the chuck 6| by pivoting the lever 61 to release the piston 4| of the chuck from fluid pressure, and a new blank can be chucked. When this new blank is identical with the previously machined blank, the machine is immediately ready for operation without requiring any fresh adjustment of parts of the machine. The control lever 9 can be brought again from its position 0 through the position I and II into the position III and the machining of the new blank is automatically effected in the manner above described. It will be recognized that the efiiciency of the machine is very high in that after adjustment of the blank and of the tool only the single main control lever 9 must be actuated in order to efiect the entire machining operations on the blank.

According to a modification it is possible to construct the piston 32 for the return of the lever 9 in such manner that the lever 9 is automatically brought back from the position III until the position IV. The above described operations during the return of the lever 9 to the position are repeated, but as soon as the backwards movement of the generating unit 6 starts, also the switch E of the rapid speed motor is actuated by the piston 35 placed immediately under fluid pressure, and the return roll of the generating drum is effected simultaneousl with the .backwards movement of the generating unit. A return of the lever 9 by hand from the position IV to the position 0 is not necessary. As soon as the rapid speed motor has been stopped a new blank can be chucked, and the lever 9 can be brought from the position IV through the positions O-I-II immediately to the position III, and the above described operations will be automatically repeated until the second cutting operation is finished and the machine is again in the starting position.

The facility of increase of the speed of the generating rolling movement of the drum is particularly advantageous when the blank is subjected to a roughing cut in a first cutting operation. However, when the cut blank for example is subjected to a successive finishing operation, it is possible to use an increased generating speed already from the beginning of the finishing cut, so that during this finishing operation no other increase of the generating rolling movement will be required. In this case the action of the second abutment It on the generating drum 5 can be suppressed when the machine is set for operation by placing the adjustable stop 88 against the stop 99 of the control piston [4 of the increased feed speed gear, so that upon movement of the auxiliary control valve 2! by the abutment I8 and upon connection of the conduit PVSl with the pressure conduit P2 the piston it cannot be displaced.

It is visible from Fig. 213 that the conduit PSFZ which connects the valve 42 with the pressure cylinder 68 operating the clamping chuck for the blank, is connected by a conduit Hi l with the conduit PVA for the valve 33 of the shutdown piston 32. This conduit m4 provides that the machine can only be started when the blank is chucked and that the drive of the machine will stop immediately when the blank would be dechucked for any possible reason. As long as the valve 32 is not in the position represented in Fig. 21) corresponding to the clamped chuck, but in the position shown in dotted lines and pressure fluid can flow through the conduit P3 into the conduit PSF2 and maintain the piston All at the left hand end of the cylinder 68 corresponding to release of the chuck, it is not possible to move the control lever 53, out of its starting position 0. The conduit PSFZ comprises a check valve U35, so that the pressure from the conduit P3, while the valve 42 is in the position shown with dotted lines, becomes effective first in, the conduit I013 before it can move the piston Al. The. pressure in the, conduit H34 and the conduit PVA causes a, movement of the pilot piston 33. towards the left so that the shut-down piston. 52 is subjected to fluid pressure and positively moves, the, lever 9 to the position 0 or the position IV, as the case may be, or when the lever B is already in the position 0, the fluid pressure acting on the piston 32 looks the piston and the lever 23 in this position, so that it cannot be brought by hand to the positions I, II or III. Onl when the valve 42 has been moved to the represented hatched position corresponding toclamping of the chuck, the conduit I04 is connected to the discharge Po, so that the piston 32 is released from fluid pressure and permits movement of the lever 9.

The auxiliary control valve 2| represented by way of example only is so constructed and the three adjustable abutments l1, l8, l9 are so disposed on the generating drum 5, that it is possible to produce bevel wheels having spiral teeth which are curved in one or the other direction, that is. to say, that the generating drum can rotate in one or the other direction to effect the generating rolling movement, and by cooperation of the three abutments with the Maltese cross 20 without any reversal of control members, except a corresponding adjustment of the abutments, the correct control operations are in tiated in both directions of rotation of the generating drum.

I claim:

1. A machine for cutting bevel gears comprising a work head unit carrying the work, a generating unit including a generating drum having a gear and carrying the tool, said two unts being relatively movable towards and away from each other, main driving means for imparting rotation to said work and said tool, a feed gear imparting the generating rolling movement to said generating drum, a pre sure fluid control sy tem includin a main control valve for controlling the operation of the machine, a single operating lever. operatively connected to said main control valve and ada ted to be brou ht by hand. from a starting position to a position corresponding to operaton of the machine, said main control valve. being act ated by the movement of said o erating lever to automatically engage said main driving means and said feed gear, an auxiliary pres.- sure fluid control valve, an adjustable abutment on said generating drum adapted to enga e and operating said auxilary control valve at the end' of the rolling movement of said generating drumv to cau e automatic return of said operating lever to starting position and actuation of said main. control valve to disengage said main driving means and feed gear.

2. A machine for cutting bevel ears as claimed in claim 1, wherein said generating drum carries a second adjustable abutment ada ted to engage, and actuate said auxiliary control valve when the tool has cut the entire depth of the tooth spaces of the gear to be produced, to cause an increase of speed of said feed gear.

3. A mach ne for cutting bevel gears asv claimed in claim 1 and comprising means for increasing the speed of said feed gear during oreration of the machine. means for preselecting the rate of increase of the feed gear speed, and a second adjustable abutment carried by said generating drum, said se ond abutment being adapted to enga e and act ate said auxiliary control valve when the tool has cut the entire depth of the tooth spaces of the gear to be produced, to cause engagement of said preselected increased speed, of the feed gear.

l. A machine for cutting bevel gears comprising a work head unit carrying the work, a generating unit including a rotatable generating drum, having a gear and carrying the tool, said two units being relatively movable towards and 1 1 away from each other, main driving means for imparting rotation to said work and to said tool, a feed gear imparting the generating rolling movement to said generating drum, means for imparting a return rolling movement at rapid speed to the generating drum, a fluid control system including a main control valve for con-.- trolling the operation of the machine, and a single operating lever coupled with said control valve for actuating said valve to automatically control said main driving means, said relative movement of the work head unit and the generating unit towards and away from each other, said feed gear for imparting generating rolling movement to said generating drum, and said return rolling movement of the generating drum when the gear generating movement is finished, said fluid control system including an auxiliary control valve, and said generating drum havin an adjustable abutment fixed thereto, said abutment being adapted to engage and actuate the auxiliary control valve at the end of the generating rolling movement of said generating drum to cause automatic movement of said operating lever and of the main control valve coupled therewith to a position in which the main control valve initiates the return rolling movement of the generating drum.

5. A machine for cutting bevel gears comprising a work head unit carrying the work, a generating unit including a generating drum having a gear and carrying the tool, said two units being relatively movable towards and away from each other, main driving means for imparting rotation to said tool and work, a feed gear imparting generating rolling movement to said generating drum, means for imparting a return rolling movement at rapid speed to the generating drum, a fluid control system including a main control valve for controlling the operaton of the ma chine, an operating lever coupled with said main control valve, an auxiliary control valve, pressure fluid operated means for automatically controlling said operating lever in response to movement of the auxiliary control Valve, an abutment on the generating drum adapted to engage and actuate the auxiliary control valve at the beginning of the generating rolling movement of the drum, and a second abutment on the generating drum adapted to engage and actuate said auxiliar control valve at the end of the generating rolling movement of the drum to cause movement of said operating lever and main control valve to a position corresponding to engagement of said rapid return rolling speed of the generating drum, whereby said first mentioned abutment will again engage and operate the auxiliary valve in reversed direction to cause return of the operating lever and the main control valve to starting position.

6. A machine for cutting bevel gears comprising a work head unit carrying the work, a generating unit including a generating drum carrying the tool, said two units being relatively movable towards and away from each other, main driving means for imparting rotation to said tool and work, a feed gear imparting generating rolling movement to said generating drum, means for imparting a return rolling movement at rapid speed to the generating drum, a fluid control system including a main control valve for control ling the operation of the machine, an operating lever coupled with said main control valve, an auxiliary control valve, pressure fluid operated means for automatically controlling said operating lever in response to movement of the auxiliary control valve, three successively arranged abutments adjustably secured to said generating drum to rotate therewith, and cam means on said auxiliary control valve adapted to be successively engaged by said three abutments during the generating rolling movement of said drum and again during the return rolling movement of said drum, each abutment imparting one movement step to said auxiliary control valve upon bein engaged with said cam means.

7. A machine for cutting bevel gears as claimed in claim 6, wherein the second of the said three successive abutments on the generating drum during the generating rolling movement of the drum moves said auxiliary control valve to cause engagement of an increase rolling speed of the drum, and the third abutment further moves the auxiliary control valve to cause dise gagement of said increased rolling speed and engagement of the return rolling speed of the generating drum.

8. A machine for cutting bevel gears according to the contnuous generating and indexing method, comprising a machine bed, a headstock rotatable on the bed, a work piece clamping chuck rotatably mounted on the headstock, a generating unit including a rotatable generating drum, a tool carrier slide mounted on the drum and movable transversely to the axis of the generating drum, and a rotatable tool carrier mounted in said slide, said generating unit and said headstock being movable towards and away from each other, a main drive motor, movement transmission means between said motor and said workpiece chuck, said generating drum and said tool carrier, a generating gear included in the movement transmission between said motor and said generating drum, an indexing gear included in the movement transmission between said motor and said work piece clamping chuck, a differential gear operatively connected with said generating gear and with said indexing gear, a feed gear for varying the speed of rolling movement imparted by the generating gear to the generate ing drum, a fluid control system including a rotary main valve and a rotary auxiliary valve for controlling the operation of the machine, a plurality of adjustable abutments circumferentially arranged on said generating drum, means mounted for rotation with said auxiliary valve and co acting with said abutments for turning said auxiliary valve into difierent control positions, a single manually operable control lever operatively connected with said main valve for imparting rotary motion thereto, fluid operated servomotor means for moving said generating unit relatively to said headstock, fluid operated clutch means for engaging and disengaging said main drive motor with and from said movement transmission means, and valve means for operating said servomotor means and clutch means in response to rotar movement of said main and auxiliary valves, whereby operation of said single control lever is efiective to control movement of said generating drum, said tool carrier, said workpiece chuck, said main drive clutch mea s and said servomotor means.

9. A machine for cutting bevel gears comprising a work head unit carrying the work, a generating unit including a rotatable generat ng drum carrying the tool, the generating unit being movable towards and away from said work head unit in the direction of the axis of the ideal crown wheel of the gear to be cut to be brought into a setting position and a Working position, a fluid control system including a main control valve for controlling the operation of the machine, a single operating lever for said control valve, pressure fluid operated clamping members for lock ing said generating unit in the working position, an adjustable stop member for limiting the movement of the generating unit towards the work head unit, a piston valve controlling the operation of said clamping members, actuating means for said piston valve operative upon abutment of the generating unit against said adjustable stop member to cause pressure fluid to be supplied to said clamping members for locking the generating unit in its working position, an overhead tie connectin the generating unit and the Work head unit, pressure fluid operated clamping members for locking said overhead tie to the two units, and pressure fluid connections between said clamping members and said piston valve to cause pressure fluid to be supplied to said clamping members to lock said overhead tie upon abutment of the generating unit against said adjustable stop member and actuation of said piston valve.

19. A machine for cutting bevel gears as claimed in claim 9, wherein said control piston for the main valve operating lever is effective in response to relief of clamping pressure on the chuck to return the operating lever to its starting position.

PAUL ASCHWANDEN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,099,674 Bullock et a1 Nov. 23, 1937 2,395,544 Galloway Feb. 26, 1946 2,398,346 Anderson Apr. 16, 1946 2,483,810 Cotta Oct. 4, 1949 2,489,227 Roehm et al Nov. 22, 1949 

